1. Field of the Invention
The invention concerns a cross flow heat exchanger unit comprising corrugated film elements stacked transversely to one another. Flow channels leading in alternating directions are thus formed, through which primary and secondary streams of cooling gas, respectively, are passed.
2. The Prior Art
Heat exchanger unis generally of this type are known, for example, from Swiss CH-PS 588 672; although the foils arranged in stacks in alternating crosswise layers reduce the weight of the heat exchanger unit, the arrangement does not provide channels favoring the flow of the medium, because of partially transverse creases. Further, as the result of the small increase in the surface area provided by the creases, the installed heat exchanger surface area is relatively low. The contact surfaces of the creases have no metallic connection with the adjacent film layers, but are separated from them by an air gap and heat conduction between the films is thus interrupted. Finally, the design lacks mechanical stability insofar as the individual film layers are interconnected only at their edges by means of folded seams, and not at their inner areas. This leads to the danger of outward buckling in the presence of certain differences in pressure between the flowing media and the environment. On the other hand, the establishment of soldered joints, customarily employed in heat exchangers made of heavier sheet metal, is either not feasible with thin films or only at a commensurably higher cost.